转换字符串型时间为long型时间

public static long getTimeFromStr(String timestr) {
        String year;
        String month;
        String day;
        String hour;
        String minute;
        String second;

        if (timestr == null || timestr.equals("")) {
            return 0;
        }

        if (timestr.length() < 4) {
            return 0;
        }
        year = timestr.substring(0, 4);

        if (timestr.length() < 7) {
            month = "1";
        } else {
            month = timestr.substring(5, 7);
        }

        if (timestr.length() < 10) {
            day = "1";
        } else {
            day = timestr.substring(8, 10);
        }

        if (timestr.length() < 13) {
            hour = "0";
        } else {
            hour = timestr.substring(11, 13);
        }

        if (timestr.length() < 16) {
            minute = "0";
        } else {
            minute = timestr.substring(14, 16);
        }

        if (timestr.length() < 19) {
            second = "0";
        } else {
            second = timestr.substring(17, 19);
        }
        int iyear = UtilTools.parseInt(year);
        int imodth = UtilTools.parseInt(month);
        int iday = UtilTools.parseInt(day);
        int ihour = UtilTools.parseInt(hour);
        int iminute = UtilTools.parseInt(minute);
        int isecond = UtilTools.parseInt(second);
        GregorianCalendar g = new GregorianCalendar(
                iyear,
                imodth - 1,
                iday,
                ihour,
                iminute,
                isecond);

        return g.getTime().getTime();
    }